GI approach to vomiting

Question 1

What is the chemoreceptor trigger zone and what receptors are there

Answer 1

Where the BBB is accessible to blood borne substances e.g toxins
Receptors include opioid, dopamine (D2), serotonin (5HT), neurokinin, histamine

Question 2

Why do animals vomit (physiology)

Answer 2

Stomulation of vomiting centre in the medulla
- Can be directly; e.g via visceral receptors and vagal afferents
- Or via chemoreceptor trigger zone

Question 3

How does metoclopramide work

Answer 3

D2 antagonist
Weak 5-HT3 antagonist

Good for central via D2 antagonism (and some peripheral effect 5-HT3) emetogens
Can have prokinetic effect

Question 4

Side effects of metoclopramide

Answer 4

Movement disorders
Extrapyramidal signs

Question 5

How does maropitant work

Answer 5

NK1 receptor antagonist
Good for both central and peripheral emetogens
= most commonly chosen

[take care in cardiac and hepatic disease, hypoproteinaemia]

Question 6

How does odansetron work

Answer 6

5-HT3 selective angstonist
So good for peripheral emetogens e.g chemical irritations to gut

Question 7

How can we broadly split up causes of vomiting

Answer 7

Gastrointestinal
Non-gastrointestinal

Question 8

Predominant features of acute gastritis

Answer 8

Sudden onset vomiting

Question 9

Prominent features of gastric ulceration or erosion

Answer 9

Vomiting, haematemesis, melaena
May have anaemia

Question 10

Prominent features of GDV

Answer 10

Non-productive retching, abdominal distension, tachycardia

Question 11

PRedominant features of chronic gastritis

Answer 11

Chronic vomiting of food o rbile

Question 12

Predominant features of delayed gastric emptying

Answer 12

Acute to chronic vomiting more than 8-10 hours after feeding

Question 13

Predominant features of GI neoplasia

Answer 13

Chronic vomiting, weight loss +/- anaemia

Question 14

What is the most common cause of chronic vomtiing in cats

Answer 14

Idiopathis inflammatory gastritis

Hyperthyroidism commonly assocaited with comiting

Question 15

What medication do cats commonly vomit after receiving

Answer 15

Alpha-2 adrenergic drugs since these receptors are important in cat vomiting centre

Question 16

What is bilious vomiting syndrome

Answer 16

Where a dog vomits bile in the morning because there is prolonged contact time between bile and gastric mucosa when stomach empty (so can’t dilute out bile) or can result from dysfunction of this area during sleep

Treat with splitting food into small feeds, including last thing at night
Could use promitlity drugs to coordinate gastric and duodenal motility
Could use sucralfate/antacids etc

Question 17

Causes of haemorrhagic gastritis

Answer 17

NSAIDs
Steroids (but rarely ulcerogenic alone)
Uraemia/renal failure
Liver disease

Question 18

What is the pathogenesis of classic IBD

Answer 18

Lymphocytic-plasmacytic inflammatory gastritis

Question 19

Treating IBD

Answer 19

immunosuppression; steroid and steroid-sparing drug e.g cyclosporine, azathioprine, chlorambucil

Question 20

Differentiating IBD from food senstivity

Answer 20

Food sensitivities resolve completely when offending food removed from diet
Biopsies are unremarkable

Question 21

What breeds are predisposed to pancreatitis and how can we work out if this is a cause of vomiting

Answer 21

= Miniature schnauzers, cocker spaniels, CCKS
- Need to correlate painful episodes and vomiting with pancreatic enzyme
elevations

Question 22

What are the bloods like on a dog with obstruction which is vomiting

Answer 22

Hypochloraemia (lose in vomit)
Metabolic alkalosis (loss of H+ in vomit + hold onto bicarbonate for electroneutrality when Cl- lost)